Polyetheretherketone (PEEK) is an attractive material for the encapsulation of active medical implants. PEEK, however, shows hydrophobic surface properties which are not favorable for protein absorption and cell adhesion. We show that oxygen rich nanofilms sticky thin film, deposited on PEEK surfaces from plasma using a plasma immersion ion implantation and deposition technique with a (CH4/O2) gas mixture greatly improved cell adhesion (up to 75%) and spreading (up to 81%). Strong correlations were found between cell adhesion and the water contact angle, the polar component of surface energy, and to a lesser extent oxygen concentration of the PEEK surfaces. Surface polarity of the plasma deposited sticky thin film was deemed to be the predominant factor in influencing cell adhesion.